[Killietalk] RO water, Hardness, Conductivity, TDS, and other related topics http://www.water-research.net/totaldissolvedsolids.htm

["Ron Schulz" <ron_schulz at gmail.com>]

Hi all,
   What is generally considered the  maximum hardness level (ppm as CaCO3)
for good egg viability of some of the softer water killies? The reason I ask
is two fold.  First, it is possible (as I believe in my case) to have  quite
low TDS but still quite high hardness levels. My well water consistently
measures 130-140ppm hardness (Lamotte test kit). It also measures about the
same  for alkalinity. The conductivity as measured on a Hach conductivity
meter is consistently in the 270-290uS/cm range.  Now....for low level
divalent species, the approx TDS (as ppm CaCO3) is  half the specific
conductance in micro seimens/cm. See reference in Subject line. So... my
water  with conductivity of 280uS/cm would have an approx TDS of 140ppm as
CaCO3. But, I already know the hardness is also 140ppm as CaCO3. Thus, I
conclude there are virtually no other  ionic species in my water. It's all
Ca and Mg carbonate and  so the TDS  is quite low but the hardness is still
pretty high. Now my killie buddy, Fred Behrmann who lives about 35 miles
from me uses surface resevoir water. It  consistently measres 35-40ppm
hardness as CaCO3  (alkalinity also 40ppm)  but the conductivity measures
about 170uS/cm. My guess is the additional ionic species comes from  NaCl as
rock salt runoff from roads. So he has a mixture of both monovalent and
divalent ions and  it  might measure at least as high as my water on a TDS
meter depending how and for what the meter was calibrated. But the actual
hardness, which is the primary factor  for egg viability (or is it?) is
almost 4X LESS. Now..... Fred gets excellent hatches of even the most
supposedly hardness sensitive killies as well as characins. How much of this
is water related?  To further complicate the matter,  I have inherited a RO
system from another killie buddy Jim Randall. Jim  recently  moved locally
but  his water source went from Mohawk River  water to surface resevoir
water. Now  it turnns out, the two resevoirs  that supply Jim and Fred are
less than 10 miles apart. I can not distinguish them apart  from simple
hardness, alkalinity, conductivity, and pH measurements.  So Jim no longer
needs the RO unit and I get to give it a try. Since I have well water, it
is pumped from my well at about 50F at a variable press or 30-60psig. Thus,
I don't get a very high a flow rate of RO water given the low press and cold
water. So, I can easily hatch all picked eggs  in low hardness water.  How
critical is this relative to the eggs being actually laid in low hardness
water?   And how low should I target. I''m thinking 2/3 RO water 1/3  well
water (resulting hardness of about  45ppm) I could  do this for the so
called sensitive species at least on a trial basis in small tanks .   Are
most of the  guys out there that have good success with some of the tougher
Aphyosemion species using either mixed RO water or have naturally very soft
water.  Also....how soft?  All responses welcome.
...........................Ron Schulz...................Dutchess  County NY
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